Watched Expose for a second time. When Ben and Juliet come to watch the monitor, Ben is asking 'who left this open' in reference to the hall they have just walked through and then ordered Juliet to 'call the flame to close it when we leave'


This suggests there is a false wall in The Pearl Station that leads to the suspected subterreanean passageway (tunnels) many of us suspected to exist. I think this is the first concrete evidence.


And speaking of concrete, I wonder if other stations had the same kind of false wall connection including The Swan, which may have been covered in concrete as Sayid noticed in season 2.

That Map Locke saw in Lockdown might have been a map of the connecting tunnels.